<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <meta http-equiv="X-UA-Compatible" content="ie=edge">
    <title>Document</title>
    <style>
        * {
            margin: 0;
            padding: 0%
        }

        html,
        body {
            height: 100%
        }

        body {
            display: flex;
        }

        section {
            width: 400px;
            height: 400px;
            background: #252525;
            margin: auto;
            border-radius: 10px;
            display: flex;
            flex-wrap: wrap;
            justify-content: space-around;
            align-items: center
        }

        section>div {
            width: 150px;
            height: 150px;
            background: #e7e7e7;
            border-radius: 10%;
            box-shadow: 5px 5px 2px #fff inset, -5px 5px 2px #d7d7d7 inset, 5px -5px 2px #bbbbbb inset, 5px 5px 2px #d7d7d7 inset;
        }

        span {
            width: 40px;
            height: 40px;
            background: black;
            border-radius: 50%;
        }

        /* 第一个 */
        section>div:nth-child(1) {
            display: flex;
            justify-content: center;
            align-items: center
        }

        /* section>div:nth-child(1) span { */
            /* 1.margin */
            /* margin: auto; */
        /* } */

        /* 第二个 */
        section>div:nth-child(2) {
            display: flex;
            justify-content: space-between;
            padding: 10px;
            box-sizing: border-box
        }

        section>div:nth-child(2) span:nth-child(2) {
            align-self: flex-end;
        }

        /* 第三个 */
        section>div:nth-child(3) {
            display: flex;
            justify-content: space-between;
            padding: 5px;
            box-sizing: border-box;
        }

        section>div:nth-child(3) span:nth-child(2) {
            align-self: center;
        }

        section>div:nth-child(3) span:nth-child(3) {
            align-self: flex-end;
        }

        /* 第四个 */
        section>div:nth-child(4) {
            display: flex;
            flex-direction: column;
            justify-content: space-between;
            padding: 10px;
            box-sizing:border-box
        }
        section>div div{
            display: flex;
            justify-content: space-between
        }
    </style>
</head>

<body>
    <section>
        <!-- 第一个 -->
        <div>
            <span></span>
        </div>
        <!-- 第二个 -->
        <div>
            <span></span><span></span>
        </div>
        <!-- 第三个 -->
        <div>
            <span></span>
            <span></span>
            <span></span>
        </div>
        <!-- 第四个 -->
        <div>
            <div>
                <span></span>
                <span></span>
            </div>
            <div><span></span>
                <span></span></div>
        </div>
    </section>
</body>

</html>